In the Long Term Evolution (LTE) system, there is generally low interference within a cell due to the use of Orthogonal Frequency Division Multiplexing (OFDM), and high inter-cell interference arising from inter-cell frequency multiplexing is predominant interference in the LTE system that results in poor performance at edges of cells. In order to improve the performance of a cell edge user, and to accommodate the required cell edge spectrum efficiency, the technology of Coordinated Multi-Point (CoMP) transmission and reception has been introduced to the Long Term Evolution-Advanced (LTE-A) system. In the CoMP technology, a plurality of adjacent base stations or nodes cooperate with each other, thereby serving a cell edge user concurrently, so as to lower same-frequency interference from an adjacent cell received by the cell edge user, and to improve the quality of service of the cell edge user, where there are generally two categories of downlink CoMP transmission technologies: the Joint Transmission (JT) and the Coordinated Scheduling/Coordinated Beam-forming (CS/CB).
For the JT technology, a serving cell and a coordinating cell transmit same Physical Downlink Shared Channel (PDSCH) data to a same User Equipment (UE) at an edge of a cell over a same time-frequency resource, due to elimination of same-frequency interference from an adjacent cell and due to superimposition of downlink signal, downlink performance of the UE at the edge of the cell is improved; for the CS technology, a serving cell transmits PDSCH downlink data to a cell edge UE, and a coordinating cell does not transmit any PDSCH data over the same time-frequency resource, thus eliminating same-frequency interference from an adjacent cell, and improving downlink performance of the UE at an edge of a cell; and for the CB technology, a serving cell and a coordinating cell transmit downlink data respectively to different UEs over a same time-frequency resource, but beam-forming of the UE in the serving cell needs to be spaced from beam-forming of the UE in the coordinating cell, to alleviate interference between them and improve downlink performance of the UEs at an edge of a cell.
Among the technologies of downlink CoMP transmission, the technologies of JT and the CS could alleviate effectively for a user at an edge of a cell same-frequency interference from another user in an adjacent cell, but an additional time-frequency resource in a coordinating cell needs to be occupied, and if the coordinating cell has a heavy load, then the average throughput of the coordinating cell may be lowered when using the technologies of JT and the CS. For the CB technology, the average throughput of the cell is not significantly affected, but a beam-forming vector of a UE in the coordinating cell needs to be adjusted, thus degrading the performance of the UE to some extent.
In view of this, the prior downlink CoMP technology, simply adopting one of the downlink CoMP transmission methods (JT, CS, or CB), fails to adapt to a varying network environment dynamically, and is unable to achieve good performance in a time-varying radio channel environment and cell load environment.